The present invention generally relates to a blade for use in conjunction with graders, snow plows and like vehicles wherein the blade travels over the surface of a substrate (e.g., the surface of a roadway) to remove snow and ice as well as other debris and material. More specifically, the present invention concerns a grader blade for use in conjunction with graders, snow plows and like vehicles wherein the blade travels over the surface of a substrate (e.g., the surface of a roadway) to remove snow and ice as well as other debris and material wherein the grader blade incorporates an insert assembly at its bottom leading edge to provide for improved impact and performance properties.
Graders and snow plows are both well known and each carry a relatively long moldboard which extends generally laterally (or across) of the substrate surface being worked by the blade. It is conventional practice to mount a grader blade on the lower edge of such moldboard with the blade, in turn, extending downwardly below the lower edge of the moldboard. The grader blade has a lower leading edge that forms the working surface of the blade. The grader (or snow plow) the moves over the surface of the substrate in a direction generally perpendicular to the length of the moldboard. The grader blade then contacts or impacts any material (e.g., snow and ice and other materials) on the surface of the substrate so as to dislodge and remove the same.
In the past, grader blades have been made of steel. Steel grader blades have the advantage of being relatively inexpensive, but also the disadvantage of wearing out rapidly since the scraping operation can be a very abrasive operation. Once worn out, one must replace the steel blade to avoid damage to the moldboard. Replacement of the steel blade is, of course, time consuming and represents downtime for the equipment. Thus, over the years, various techniques, such as impregnation and hardfacing of the blade cutting edge with carbide particles. For example, cemented carbide inserts can be attached into or onto the blade edge in an attempt to prolong the life of the steel blade. Earlier prior art grader blades includes those shown and described in the following patent documents: U.S. Pat. No. 1,922,917 to Russell et al., U.S. Pat. No. 3,529,677 to Stephenson, U.S. Pat. No. 3,790,353 to Jackson et al.,), U.S. Pat. No. 3,971,323 to Beiswenger, U.S. Pat. No. 3,888,027 to Toews, U.S. Pat. No. 3,934,654 to Stephenson et al.,) and U.S. Pat. No. 4,052,802 to Moen et al. A similar type of blade where a cemented carbide inserts can be attached into or onto the blade edge is a blade identified as a Kengard A grader blade manufactured by Kennametal Inc. of Latrobe, Pa. 15650 United States of America.
In addition to the above described grader blades, U.S. Pat. No. 4,715,450 to Hallissy et al. discloses a grader blade that presents a casting-insert assembly at the bottom leading edge thereof. The following excerpt (Col. 4, lines 4 through 18) from the '450 Hallissy et al. patent describes the blade structure:                The grader blade 18 includes a casted assembly, generally indicated by numeral 38, being composed of a rear preformed cemented carbide insert 40 and a front casted layer 42 of carbide grit in combination with a substrate 44 of casting material. The substrate 44 holds the insert 40 and layer 42 in a tiered contacting and attached relationship with one another. The casted assembly 38 is disposed in the recess 36 and the substrate 44 is welded to the body 20 such that the casted assembly 38, the insert 40 and layer 42, extend beyond the front and bottom surfaces 30,34 of the body edge 28 for contacting the surface being worked. In actuality, the casted layer 42 of carbide grit is disposed substantially outside of the recess 36 and forwardly of the front surface 30 on the steel body 20.        
Further, U.S. Pat. No. 4,770,253 to Hallissy et al. discloses a grader blade. The Abstract from the '253 Hallissy et al. patent describes this grader blade structure:                A grader blade has a steel body with a bottom edge incorporating a pair of tiered, elongated carbide inserts in a forward portion thereof. The carbide inserts, being arranged in a tiered contacting relationship, are disposed in a stepped recess formed in and along the forward portion of the bottom edge of the blade body and brazed to the blade body and to each other so as to project forwardly and downwardly from the recess. A front one of the tiered inserts is composed of a cemented carbide composition having a high cobalt content, for instance 20 percent by weight, adapting it for enhanced impact wear resistance, whereas a rear one of the tiered inserts is composed of a cemented carbide composition having a low cobalt content, for instance 11.5 percent by weight, adapting it for enhanced downpressure wear resistance.        
While many of these grader blades appear to operate reasonably well under the operating conditions for which they were designed, most grader blades seem to embody one or more shortcomings in terms of complexity, performance, reliability and cost effectiveness. In reference to the structure as disclosed in U.S. Pat. No. 4,770,253 to Hallissy et al., the trailing insert has the tendency to fracture prematurely. When this happens, the trailing insert falls off the blade thereby leaving the leading insert to absorb all of the impacts, as well as provide the wear resistance to the grader blade.
There remains a need to provide an improved grade blade structure that exhibits acceptable performance properties. In this regard, it would be desirable to provide an improved grader blade that more adequately addresses the kinds of wear and forces encountered by the bottom leading edge of the grader blade.
It would also be desirable to provide an improved grader blade that provides improved impact wear resistance. It would also be desirable to provide an improved grader blade that provides improved fracture wear resistance. It would also be desirable to provide an improved grader blade that provides improved abrasion wear resistance. It would also be desirable to provide an improved grader blade that provides improved down-pressure wear resistance.